Nonvolatile semiconductor memory device and method of manufacturing the same

ABSTRACT

A nonvolatile semiconductor memory device comprises a memory string, and a wiring. The memory string comprises a semiconductor layer, a charge storage layer, and a plurality of first conductive layers. The plurality of first conductive layers comprises a stepped portion formed in a stepped shape such that positions of ends of the plurality of first conductive layers differ from one another. The wiring comprises a plurality of second conductive layers extending upwardly from an upper surface of the first conductive layers comprising the stepped portion. The plurality of second conductive layers are formed such that upper ends thereof are aligned with a surface parallel to the substrate, and such that a diameter thereof decreases from the upper end thereof to a lower end thereof. The plurality of second conductive layers are formed such that the greater a length thereof in the perpendicular direction, the larger a diameter of the upper end thereof.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority fromprior Japanese Patent Application No. 2009-42748, filed on Feb. 25,2009, the entire contents of which are incorporated herein by reference.

BACKGROUND

In recent years, there are proposed many semiconductor memory devices inwhich memory cells are disposed three-dimensionally in order to increasea degree of integration of memory.

One conventional semiconductor memory device in which memory cells aredisposed three-dimensionally uses a transistor with a cylindrical columntype structure (refer to J.P. 2007-266143). The semiconductor memorydevice using the transistor with a cylindrical column type structure isprovided with a stacked conductive layer stacked in multiple layers andconfigured to form a gate electrode, and a pillar-shaped columnarsemiconductor. The columnar semiconductor functions as a channel (body)portion of the transistor. A vicinity of the columnar semiconductor isprovided with a memory gate insulating layer capable of storing acharge. A configuration including these stacked conductive layers, thecolumnar semiconductor, and the memory gate insulating layer is called amemory string.

To achieve conduction with a peripheral circuit in a semiconductormemory device having the above-described memory string, a contact plugis formed extending in a stacking direction (direction perpendicular toa substrate) from the stacked conductive layer. Generally, the contactplug is formed by the following process. That is, first, an interlayerinsulating layer is formed so as to cover the stacked conductive layer.Subsequently, the interlayer insulating layer is penetrated so as toreach an upper surface of the respective stacked conductive layers,thereby forming a hole. Then, a conductive layer is deposited so as tofill the hole, thereby forming the contact plug.

However, the above-described manufacturing process causes the contactplug to be formed in a tapered shape in which a diameter of the contactplug becomes smaller from an upper end to a lower end thereof.Accordingly, the lower the layer in which the contact plug has its lowerend, the more difficult it becomes, during manufacture, to fill the holewith the conductive layer. In addition, the lower the layer in which thecontact plug has its lower end, the more difficult it becomes, duringmanufacture, to form the hole completely penetrating the interlayerinsulating layer. Moreover, the lower the layer in which the contactplug has its lower end, the smaller becomes a contact area with thestacked conductive layer. It is difficult to manufacture a nonvolatilesemiconductor memory device having a high reliability using theabove-described manufacturing process.

SUMMARY

In accordance with an aspect of the present invention, a nonvolatilesemiconductor memory device comprises: a memory string having aplurality of electrically rewritable memory cells connected in series;and a wiring connected to a control electrode of the memory cells, thememory string comprising: a semiconductor layer including a columnarportion extending in a perpendicular direction with respect to asubstrate; a charge storage layer formed on a side surface of thecolumnar portion; and a plurality of first conductive layers formed onthe charge storage layer, and configured to function as a controlelectrode of the memory cells, the plurality of first conductive layerscomprising a stepped portion formed in a stepped shape such thatpositions of an ends of the plurality of first conductive layers differfrom one another, and the wiring comprising a plurality of secondconductive layers extending upwardly from an upper surface of the firstconductive layers comprising the stepped portion, the plurality ofsecond conductive layers being formed such that upper ends thereof arealigned with a surface parallel to the substrate, and such that adiameter thereof decreases from the upper end thereof to a lower endthereof, and the plurality of second conductive layers being formed suchthat the greater a length thereof in the perpendicular direction, thelarger a diameter of the upper end thereof.

In accordance with an of the present invention, a nonvolatilesemiconductor memory device comprises: a memory string having aplurality of electrically rewritable memory cells connected in series;and a wiring connected to a control electrode of the memory cells, thememory string comprising: a semiconductor layer including a columnarportion extending in a perpendicular direction with respect to asubstrate; a charge storage layer formed on a side surface of thecolumnar portion; and a plurality of first conductive layers formed onthe charge storage layer, and configured to function as a controlelectrode of the memory cells, the plurality of first conductive layerscomprising a stepped portion formed in a stepped shape such thatpositions of an ends of the plurality of first conductive layers differfrom one another, and the wiring comprising a plurality of secondconductive layers extending upwardly from an upper surface of the firstconductive layers comprising the stepped portion, the plurality ofsecond conductive layers being formed such that an upper ends thereofare aligned with a surface parallel to the substrate, and a ratio of aheight of the second conductive layer and a diameter of a lower end ofthe second conductive layer being constant among the plurality of secondconductive layers.

In accordance with an aspect of the present invention, a method ofmanufacturing a nonvolatile semiconductor memory device, the nonvolatilesemiconductor memory device including a plurality of memory strings eachhaving a plurality of electrically rewritable memory cells connected inseries, comprises: depositing a plurality of first conductive layers ona substrate; penetrating the plurality of first conductive layers toform a penetration hole; forming a charge storage layer on a sidesurface facing the penetration hole; forming a semiconductor layer so asto fill the penetration hole; configuring a stepped portion formed in astepped shape in the plurality of first conductive layers such that aposition of an end of the plurality of first conductive layers differs;and forming a plurality of second conductive layers extending upwardlyfrom an upper surface of the first conductive layers configuring thestepped portion, the plurality of second conductive layers being formedsuch that an upper end thereof is aligned with a surface parallel to thesubstrate, and such that a diameter thereof decreases from the upper endthereof to a lower end thereof, and being formed such that the greater alength thereof in the perpendicular direction, the larger a diameter ofthe upper end thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a nonvolatile semiconductor memory device100 in accordance with a first embodiment.

FIG. 2 is a circuit diagram of a memory cell array 11.

FIG. 3 is a schematic perspective view of the memory cell array 11.

FIG. 4 is a cross-sectional view showing one end in a row direction ofFIG. 3.

FIG. 5 is a cross-sectional view showing the other end in the rowdirection of FIG. 3.

FIG. 6 is an enlarged view of FIG. 4.

FIG. 7A is a top view showing a first contact plug layer 54 and a secondcontact plug layer 55 a.

FIG. 7B is a top view showing second contact plug layers 55 b-55 g.

FIGS. 8-28 are cross-sectional views showing a manufacturing process ofthe nonvolatile semiconductor memory device 100 in accordance with thefirst embodiment.

FIG. 29 is a cross-sectional view showing a nonvolatile semiconductormemory device in accordance with a second embodiment.

FIGS. 30-38 are cross-sectional views showing a manufacturing process ofthe nonvolatile semiconductor memory device in accordance with thesecond embodiment.

FIG. 39 is a cross-sectional view showing a nonvolatile semiconductormemory device in accordance with a third embodiment.

FIG. 40 is a cross-sectional view showing a nonvolatile semiconductormemory device in accordance with a fourth embodiment.

FIG. 41 is a top view showing second contact plug layers 55Ab-55Ag in anonvolatile semiconductor memory device in accordance with a fifthembodiment.

FIG. 42 is a top view showing the second contact plug layers 55Ab-55Agin a nonvolatile semiconductor memory device in accordance with a sixthembodiment.

FIG. 43 is a top view showing second contact plug layers 55Bb-55Bg in anonvolatile semiconductor memory device in accordance with a seventhembodiment.

FIG. 44 is a top view showing second wiring layers 53Ab-53Ag in thenonvolatile semiconductor memory device in accordance with the seventhembodiment.

FIG. 45 is a top view showing second wiring layers 53Bb-53Bg in anonvolatile semiconductor memory device in accordance with an eighthembodiment.

FIG. 46 is a top view showing second contact plug layers 55Cb-55Cg in anonvolatile semiconductor memory device in accordance with a ninthembodiment.

FIG. 47 is a top view showing the second contact plug layers 55Cb-55Cgin a nonvolatile semiconductor memory device in accordance with a tenthembodiment.

DETAILED DESCRIPTION

Embodiments of a nonvolatile semiconductor memory device in accordancewith the present invention are described below with reference to thedrawings.

First Embodiment

(Configuration of a Nonvolatile Semiconductor Memory Device 100)

First, a configuration of a nonvolatile semiconductor memory device 100in accordance with a first embodiment is described with reference toFIG. 1. FIG. 1 is a block diagram of the nonvolatile semiconductormemory device 100 in accordance with the first embodiment.

As shown in FIG. 1, the nonvolatile semiconductor memory device 100 inaccordance with the first embodiment comprises a memory cell array 11,row decoders 12 and 13, a sense amplifier 14, a column decoder 15, and acontrol signal generating section (high voltage generating section) 16.

The memory cell array 11 includes memory transistors MTr1-MTr4configured to store data electrically. The row decoders 12 and 13 decodea block address signal and so on downloaded thereto and control thememory cell array 11. The sense amplifier 14 reads data from the memorycell array 11. The column decoder 15 decodes a column address signal andcontrols the sense amplifier 14. The control signal generating section16 generates a high voltage required during write and erase by boostinga power supply voltage, and, in addition, generates a control signal andcontrols the row decoders 12 and 13, the sense amplifier 14, and thecolumn decoder 15.

Next, a circuit configuration of the memory cell array 11 is describedwith reference to FIG. 2. FIG. 2 is a circuit diagram of the memory cellarray 11. As shown in FIG. 2, the memory cell array 11 includes aplurality of memory blocks MB. The memory blocks MB are arranged in acolumn direction on a semiconductor substrate Ba (not shown). In otherwords, the memory blocks MB are formed in certain regions on thesemiconductor substrate Ba.

As shown in FIG. 2, the memory block MB comprises a plurality of memorystrings MS, source side select transistors SSTr, and drain side selecttransistors SDTr. The memory string MS is configured by memorytransistors MTr1-MTr4 connected in series. The drain side selecttransistor SDTr is connected to one end of the memory string MS (memorytransistor MTr4). The source side select transistor SSTr is connected tothe other end of the memory string MS (memory transistor MTr1). Forexample, each individual memory block MB has the memory strings MSprovided in a matrix formation over a plurality of rows and columns.Note that each of the memory string MS may be configured by more thanfour memory transistors.

As shown in FIG. 2, in the memory block MB, a control gate of the memorytransistors MTr1 arranged in the matrix formation is commonly connectedto the word line WL1. Similarly, a control gate of the memorytransistors MTr2 is commonly connected to the word line WL2; a controlgate of the memory transistors MTr3 is commonly connected to the wordline WL3; and a control gate of the memory transistors MTr4 is commonlyconnected to the word line WL4.

As shown in FIG. 2, in the memory block MB, a control gate of each ofthe drain side select transistors SDTr arranged in a line in a rowdirection is commonly connected to a drain side select gate line SGD.The drain side select gate line SGD is formed so as to extend in the rowdirection. In one memory block MB, a plurality of drain side select gatelines SGD are provided with a certain pitch in the column direction. Inaddition, another end of the drain side select transistor SDTr arrangedin a line in the column direction is commonly connected to a bit lineBL. The bit line BL is formed so as to extend in the column direction. Aplurality of bit lines BL is provided in the row direction.

As shown in FIG. 2, a control gate of all the source side selecttransistors SSTr in one memory block MB is commonly connected to asource side select gate line SGS. In addition, another end of the sourceside select transistor SSTr arranged in the column direction is commonlyconnected to a source line SL.

The above-described circuit configuration of the memory cell array 11 isrealized by a stacking structure shown in FIGS. 3-5. FIG. 3 is aschematic perspective view of the memory cell array 11. FIG. 4 is across-sectional view showing one end in the row direction of FIG. 3.FIG. 5 is a cross-sectional view showing the other end in the rowdirection of FIG. 3.

The memory cell array 11 includes, for each of the memory blocks MB, asource side select transistor layer 20, a memory transistor layer 30, adrain side select transistor layer 40, and a wiring layer 50, stackedsequentially on the semiconductor substrate Ba, as shown in FIGS. 3-5.

The source side select transistor layer 20 is a layer which functions asthe source side select transistor SSTr. The memory transistor layer 30is a layer which functions as the memory string MS (memory transistorsMTr1-MTr4). The drain side select transistor layer 40 is a layer whichfunctions as the drain side select transistor SDTr. The wiring layer 50is a layer which functions as various wirings.

The semiconductor substrate Ba includes on an upper surface thereof adiffusion layer Ba1, as shown in FIGS. 3-5. The diffusion layer Ba1functions as the source line SL.

The source side select transistor layer 20 includes a source side firstinsulating layer 21, a source side conductive layer 22, a source sidesecond insulating layer 23, a protective insulating layer 24, and aninterlayer insulating layer 25, as shown in FIGS. 3-5. The source sideconductive layer 22 functions as the source side select gate line SGS.In addition, the source side conductive layer 22 functions as a controlelectrode of the source side select transistor SSTr.

The source side first insulating layer 21, the source side conductivelayer 22, and the source side second insulating layer 23 are formedsequentially on the semiconductor substrate Ba, as shown in FIGS. 3-5.The source side conductive layer 22 is formed so as to extendtwo-dimensionally in the row direction and the column direction (in aplate-like shape) along the memory block MB.

The source side first insulating layer 21, the source side conductivelayer 22, and the source side second insulating layer 23 have an endthereof in the row direction formed protruding further in the rowdirection than an end of a word line conductive layer 31 a describedhereafter by an amount of a certain width L1, as shown in FIG. 4. Inother words, the end of the source side first insulating layer 21, thesource side conductive layer 22, and the source side second insulatinglayer 23 configures a stepped portion ST (step ST0) having a steppedshape, similarly to word line conductive layers 31 a-31 d describedhereafter. Moreover, the step ST0 has the certain width L1 in the rowdirection.

The protective insulating layer 24 is formed so as to cover the sourceside first insulating layer 21, the source side conductive layer 22, andthe source side second insulating layer 23 (step ST0), as shown in FIG.4. The interlayer insulating layer 25 is formed so as to bury the sourceside first insulating layer 21, the source side conductive layer 22, thesource side second insulating layer 23, and the protective insulatinglayer 24. An upper surface of the interlayer insulating layer 25 isformed parallel to the semiconductor substrate Ba.

The source side first insulating layer 21, the source side secondinsulating layer 23, and the interlayer insulating layer 25 areconstituted by, for example, silicon oxide (SiO₂). The source sideconductive layer 22 is constituted by, for example, polysilicon (p-Si).The protective insulating layer 24 is constituted by, for example,silicon nitride (SiN).

Moreover, as shown in FIGS. 4 and 5, the source side select transistorlayer 20 includes a source side hole 26 formed so as to penetrate thesource side first insulating layer 21, the source side conductive layer22, and the source side second insulating layer 23. The source side hole26 is formed in a matrix in the row direction and the column direction.The source side hole 26 is formed at a position aligning with thediffusion region Ba1.

Additionally, as shown in FIGS. 4 and 5, the source side selecttransistor layer 20 includes a source side gate insulating layer 27 anda source side columnar semiconductor layer 28 formed sequentially on aside wall of the source side hole 26. The source side gate insulatinglayer 27 is formed with a certain thickness on the side wall of thesource side hole 26. The source side columnar semiconductor layer 28 isformed so as to fill the source side hole 26. The source side columnarsemiconductor layer 28 is formed in a column shape extending in astacking direction. An upper surface of the source side columnarsemiconductor layer 28 is formed so as to be in contact with a lowersurface of a memory columnar semiconductor layer 37 described hereafter.

The source side gate insulating layer 27 is constituted by, for example,silicon oxide (SiO₂). The source side columnar semiconductor layer 28 isconstituted by, for example, polysilicon (p-Si).

The memory transistor layer 30 includes the word line conductive layers31 a-31 d and inter-word line insulating layers 32 a-32 d, a protectiveinsulating layer 33, and an interlayer insulating layer 34, stackedsequentially on the source side select transistor layer 20, as shown inFIGS. 4 and 5. The word line conductive layers 31 a-31 d function asword lines WL1-WL4. In addition, the word line conductive layers 31 a-31d function as a control electrode of the memory transistors MTr1-MTr4.

The word line conductive layers 31 a-31 d and the inter-word lineinsulating layers 32 a-32 d are formed so as to extend two-dimensionallyin the row direction and the column direction (in a plate-like shape).The word line conductive layers 31 a-31 d and the inter-word lineinsulating layers 32 a-32 d are stacked alternately and divided intomemory blocks MB. The protective insulating layer 33 is formed so as tocover the word line conductive layers 31 a-31 d and the inter-word lineinsulating layers 32 a-32 d, and to be continuous in an integratedmanner with the protective insulating layer 24. The interlayerinsulating layer 34 is formed so as to bury the word line conductivelayers 31 a-31 d, the inter-word line insulating layers 32 a-32 d, andthe protective insulating layer 33, and to be continuous in anintegrated manner with the interlayer insulating layer 25.

As shown in FIGS. 3 and 4, the word line conductive layers 31 a-31 d andthe inter-word line insulating layers 32 a-32 d are formed in a steppedshape such that positions of ends thereof in the row direction differfrom one another. That is, the ends in the row direction of the wordline conductive layers 31 a-31 d and the inter-word line insulatinglayers 32 a-32 d configure a stepped portion ST with the ends formed ina stepped shape. The stepped portion ST is formed so as to descend inthe row direction towards an end of the memory block MB. The steppedportion ST includes steps ST1-ST4 arranged in a line in the rowdirection. Besides, each of the sides of the steps ST1-ST4 faces the rowdirection.

The steps ST1-ST4 are provided adjacently in the row directionproceeding from an end vicinity of the memory block MB towards thecenter of the memory block MB, as shown in FIGS. 3 and 4. The step ST1is provided above the step ST0; the step ST2 is provided above the stepST1; the step ST3 is provided above the step ST2; and the step ST4 isprovided above the step ST3.

The steps ST1-ST4 are each configured by a stacked structure of oneconductive layer and one insulating layer, as shown in FIG. 4. That is,the step ST1 is configured by an end of the word line conductive layer31 a and an end of the inter-word line insulating layer 32 a; the stepST2 is configured by an end of the word line conductive layer 31 b andan end of the inter-word line insulating layer 32 b; the step ST3 isconfigured by an end of the word line conductive layer 31 c and an endof the inter-word line insulating layer 32 c; and the step ST4 isconfigured by an end of the word line conductive layer 31 d and an endof the inter-word line insulating layer 32 d. As shown in FIG. 4, thesteps ST1-ST4 are formed with a certain width L1 in the row direction.The protective insulating layer 33 is formed so as to cover the stepsST1-ST4. An upper surface of the interlayer insulating layer 34 isformed parallel to the semiconductor substrate Ba.

The word line conductive layers 31 a-31 d are constituted by, forexample, polysilicon (p-Si). The inter-word line insulating layers 32a-32 d and the interlayer insulating layer 34 are constituted by, forexample, silicon oxide (SiO₂). The protective insulating layer 33 isconstituted by, for example, silicon nitride (SiN).

Moreover, as shown in FIGS. 4 and 5, the memory transistor layer 30includes a memory hole 35 formed so as to penetrate the word lineconductive layers 31 a-31 d and the inter-word line insulating layers 32a-32 d. The memory hole 35 is formed in a matrix in the row directionand the column direction. The memory hole 35 is formed at a positionaligning with the source side hole 26.

Additionally, as shown in FIGS. 4 and 5, the memory transistor layer 30includes a memory gate insulating layer 36 and a memory columnarsemiconductor layer 37, stacked sequentially on a side wall of thememory hole 35. FIG. 6 here is an enlarged view of FIG. 4.

As shown in FIG. 6, the memory gate insulating layer 36 is configured bya block insulating layer 36 a, a charge storage layer 36 b, and a tunnelinsulating layer 36 c. The block insulating layer 36 a is formed with acertain thickness on the side wall of the memory hole 35, as shown inFIG. 6. The charge storage layer 36 b is formed with a certain thicknesson a side wall of the block insulating layer 36 a. The tunnel insulatinglayer 36 c is formed with a certain thickness on a side wall of thecharge storage layer 36 b. The memory columnar semiconductor layer 37 isformed so as to fill the memory hole 35. The memory columnarsemiconductor layer 37 is formed in a column shape extending in thestacking direction. The lower surface of the memory columnarsemiconductor layer 37 is formed so as to be in contact with the uppersurface of the source side columnar semiconductor layer 28. Moreover, anupper surface of the memory columnar semiconductor layer 37 is formed soas to be in contact with a lower surface of a drain side columnarsemiconductor layer 47 described hereafter.

The block insulating layer 36 a and the tunnel insulating layer 36 c areconstituted by, for example, silicon oxide (SiO₂). The charge storagelayer 36 b is constituted by, for example, silicon nitride (SiN). Thememory columnar semiconductor layer 37 is constituted by, for example,polysilicon (p-Si).

The drain side select transistor layer 40 includes a drain sideconductive layer 41, a drain side insulating layer 42, a protectiveinsulating layer 43, and an interlayer insulating layer 44, stacked onthe memory transistor layer 30, as shown in FIGS. 4 and 5. The drainside conductive layer 41 functions as the drain side select gate lineSGD. In addition, the drain side conductive layer 41 functions as acontrol gate of the drain side select transistor SDTr.

As shown in FIGS. 4 and 5, the drain side conductive layer 41 and thedrain side insulating layer 42 are formed directly above the memorycolumnar semiconductor layer 37. The drain side conductive layer 41 andthe drain side insulating layer 42 are formed in stripes extending inthe row direction and having a certain pitch in the column direction.The drain side conductive layer 41 and the drain side insulating layer42 are formed shorter in the row direction than the word line conductivelayer 31 d. In other words, an end of the drain side conductive layer 41and the drain side insulating layer 42 in the row direction configures astepped portion ST (step ST5) having a stepped shape, similarly to theword line conductive layers 31 a-31 d. The step ST5 is positionedupwardly of the step ST4. The protective insulating layer 43 is formedso as to cover the step ST5. An upper surface of the interlayerinsulating layer 44 is formed parallel to the semiconductor substrateBa.

As shown in FIGS. 4 and 5, the drain side insulating layer 42 is formedon an upper surface of the drain side conductive layer 41. Theprotective insulating layer 43 is formed so as to cover the drain sideconductive layer 41 and the drain side insulating layer 42, and to becontinuous in an integrated manner with the protective insulating layer33. The interlayer insulating layer 44 is formed to a certain height soas to bury the drain side conductive layer 41, the drain side insulatinglayer 42, and the protective insulating layer 43, and to be continuousin an integrated manner with the interlayer insulating layer 34.

The drain side conductive layer 41 is constituted by, for example,polysilicon (p-Si). The drain side insulating layer 42 and theinterlayer insulating layer 44 are constituted by, for example, siliconoxide (SiO₂). The protective insulating layer 43 is constituted by, forexample, silicon nitride (SiN).

Moreover, as shown in FIGS. 4 and 5, the drain side select transistorlayer 40 includes a drain side hole 45 formed so as to penetrate thedrain side conductive layer 41 and the drain side insulating layer 42.The drain side hole 45 is formed in a matrix in the row direction andthe column direction. The drain side hole 45 is formed at a positionaligning with the memory hole 35.

Additionally, as shown in FIGS. 4 and 5, the drain side selecttransistor layer 40 includes a drain side gate insulating layer 46 and adrain side columnar semiconductor layer 47 formed sequentially on a sidewall of the drain side hole 45. The drain side gate insulating layer 46is formed with a certain thickness on the side wall of the drain sidehole 45. The drain side columnar semiconductor layer 47 is formed so asto fill the drain side hole 45. The drain side columnar semiconductorlayer 47 is formed in a column shape extending in the stackingdirection. The lower surface of the drain side columnar semiconductorlayer 47 is formed so as to be in contact with the upper surface of thememory columnar semiconductor layer 37.

The drain side gate insulating layer 46 is constituted by, for example,silicon oxide (SiO₂). The drain side columnar semiconductor layer 47 isconstituted by, for example, polysilicon (p-Si).

The wiring layer 50 includes an interlayer insulating layer 51, a firstwiring layer 52, second wiring layers 53 a-53 g, a first contact pluglayer 54, and second contact plug layers 55 a-55 g, as shown in FIGS. 4and 5. The first wiring layer 52 functions as the bit line BL.

The interlayer insulating layer 51 is formed on an upper layer of theinterlayer insulating layer 44, as shown in FIGS. 4 and 5.

The first wiring layer 52 and the second wiring layers 53 a-53 g areformed so as to fill a trench 56, as shown in FIGS. 4 and 5. The trench56 is formed so as to penetrate the interlayer insulating layer 51.

The first wiring layer 52 includes a barrier metal layer 2A and a metallayer 2B. The barrier metal layer 2A is provided to prevent diffusion ofthe metal layer 2B. The barrier metal layer 2A is formed with a certainthickness on a side surface facing the trench 56. The metal layer 2B isformed so as to be in contact with the barrier metal layer 2A and tofill the trench 56.

The second wiring layers 53 a-53 g include barrier metal layers 3 aA-3gA and metal layers 3 aB-3 gB. The barrier metal layers 3 aA-3 gA areprovided to prevent diffusion of the metal layers 3 aB-3 gB. The barriermetal layers 3 aA-3 gA are formed with a certain thickness on the sidesurface facing the trench 56. The metal layers 3 aB-3 gB are formed soas to be in contact with the barrier metal layers 3 aA-3 gA and to fillthe trench 56.

The barrier metal layers 2A and 3 aA-3 gA are constituted from a metalsuch as tantalum (Ta), titanium (Ti), tungsten (W), ruthenium (Ru), ormanganese (Mn), or from a metal compound thereof. The metal layers 2Band 3 aB-3 gB are constituted by any of tungsten (W), copper (Cu), andaluminum (Al).

The first contact plug layer 54 is formed so as to fill a hole 57, asshown in FIGS. 4 and 5. The hole 57 is formed so as to extend from theupper surface of the interlayer insulating layer 44 as far as an uppersurface of the drain side columnar semiconductor layer 47. The firstcontact plug layer 54 is formed at a position aligning with the drainside columnar semiconductor layer 47. The first contact plug layer 54 isformed in a column shape so as to be in contact with the upper surfaceof the drain side columnar semiconductor layer 47 and a lower surface ofthe first wiring layer 52. An upper surface of the first contact pluglayer 54 is formed in alignment with a surface of the interlayerinsulating layer 44.

The second contact plug layer 55 a is formed so as to fill a hole 58 a,as shown in FIG. 5. The hole 58 a is formed so as to extend from theupper surface of the interlayer insulating layer 44 as far as the uppersurface of the drain side conductive layer 41 (step ST5). The secondcontact plug layer 55 a is formed so as to be in contact with the uppersurface of the drain side conductive layer 41 (step ST5) and a lowersurface of the second wiring layer 53 a. The second contact plug layer55 a is formed longer in the stacking direction than the first contactplug layer 54 and has an upper surface thereof formed in alignment withthe surface of the interlayer insulating layer 44.

The second contact plug layer 55 b is formed so as to fill a hole 58 b,as shown in FIG. 4. The hole 58 b is formed so as to extend from theupper surface of the interlayer insulating layer 44 as far as an uppersurface of the word line conductive layer 31 d (step ST4). The secondcontact plug layer 55 b is formed so as to be in contact with the uppersurface of the word line conductive layer 31 d (step ST4) and a lowersurface of the second wiring layer 53 b. The second contact plug layer55 b is formed longer in the stacking direction than the second contactplug layer 55 a and has an upper surface thereof formed in alignmentwith the surface of the interlayer insulating layer 44.

The second contact plug layer 55 c is formed so as to fill a hole 58 c,as shown in FIG. 4. The hole 58 c is formed so as to extend from theupper surface of the interlayer insulating layer 44 as far as an uppersurface of the word line conductive layer 31 c (step ST3). The secondcontact plug layer 55 c is formed so as to be in contact with the uppersurface of the word line conductive layer 31 c (step ST3) and a lowersurface of the second wiring layer 53 c. The second contact plug layer55 c is formed longer in the stacking direction than the second contactplug layers 55 a and 55 b and has an upper surface thereof formed inalignment with the surface of the interlayer insulating layer 44.

The second contact plug layer 55 d is formed so as to fill a hole 58 d,as shown in FIG. 4. The hole 58 d is formed so as to extend from theupper surface of the interlayer insulating layer 44 as far as an uppersurface of the word line conductive layer 31 b (step ST2). The secondcontact plug layer 55 d is formed so as to be in contact with the uppersurface of the word line conductive layer 31 b (step ST2) and a lowersurface of the second wiring layer 53 d. The second contact plug layer55 d is formed longer in the stacking direction than the second contactplug layers 55 a-55 c and has an upper surface thereof formed inalignment with the surface of the interlayer insulating layer 44.

The second contact plug layer 55 e is formed so as to fill a hole 58 e,as shown in FIG. 4. The hole 58 e is formed so as to extend from theupper surface of the interlayer insulating layer 44 as far as an uppersurface of the word line conductive layer 31 a (step ST1). The secondcontact plug layer 55 e is formed so as to be in contact with the uppersurface of the word line conductive layer 31 a (step ST1) and a lowersurface of the second wiring layer 53 e. The second contact plug layer55 e is formed longer in the stacking direction than the second contactplug layers 55 a-55 d and has an upper surface thereof formed inalignment with the surface of the interlayer insulating layer 44.

The second contact plug layer 55 f is formed so as to fill a hole 58 f,as shown in FIG. 4. The hole 58 f is formed so as to extend from theupper surface of the interlayer insulating layer 44 as far as an uppersurface of the source side conductive layer 22 (step ST0). The secondcontact plug layer 55 f is formed so as to be in contact with the uppersurface of the source side conductive layer 22 (step ST0) and a lowersurface of the second wiring layer 53 f. The second contact plug layer55 f is formed longer in the stacking direction than the second contactplug layers 55 a-55 e and has an upper surface thereof formed inalignment with the surface of the interlayer insulating layer 44.

The second contact plug layer 55 g is formed so as to fill a hole 58 g,as shown in FIG. 4. The hole 58 g is formed so as to extend as far as anupper surface of the diffusion layer Ba1 on the semiconductor substrateBa. The second contact plug layer 55 g is formed so as to be in contactwith the upper surface of the diffusion layer Ba1 on the semiconductorsubstrate Ba and a lower surface of the second wiring layer 53 g. Thesecond contact plug layer 55 g is formed longer in the stackingdirection than the second contact plug layers 55 a-55 f and has an uppersurface thereof formed in alignment with the surface of the interlayerinsulating layer 44.

The first contact plug layer 54 includes a barrier metal layer 4A and ametal layer 4B. The barrier metal layer 4A is provided to preventdiffusion of the metal layer 4B. The barrier metal layer 4A is formedwith a certain thickness on a side surface of the hole 57. The metallayer 4B is formed so as to be in contact with the barrier metal layer4A and to fill the hole 57.

The second contact plug layers 55 a-55 g include barrier metal layers 5aA-5 gA and metal layers 5 aB-5 gB. The barrier metal layers 5 aA-5 gAare provided to prevent diffusion of the metal layers 5 aB-5 gB. Thebarrier metal layers 5 aA-5 gA are formed with a certain thickness onthe side surface of the holes 58 a-58 g. The metal layers 5 aB-5 gB areformed so as to be in contact with the barrier metal layers 5 aA-5 gAand to fill the holes 58 a-58 g.

The barrier metal layers 4A and 5 aA-5 gA are constituted from a metalsuch as tantalum (Ta), titanium (Ti), tungsten (W), ruthenium (Ru), ormanganese (Mn), or from a metal compound thereof. The metal layers 4Band 5 aB-5 gB are constituted by any of tungsten (W), copper (Cu), andaluminum (Al). The interlayer insulating layer 51 is constituted bysilicon oxide (SiO₂)

Next, a shape and a position of formation of the first contact pluglayer 54 and the second contact plug layers 55 a-55 g are specificallyexplained with reference to FIGS. 7A and 7B. FIG. 7A is a top viewshowing the first contact plug layer 54 and the second contact pluglayer 55 a, and FIG. 7B is atop view showing the second contact pluglayers 55 b-55 g.

As shown in FIGS. 7A and 7B, the first contact plug layer 54 and thesecond contact plug layers 55 a-55 g are formed in a tapered shape suchthat a diameter thereof decreases from an upper end thereof to a lowerend thereof. Moreover, the upper end of the first contact plug layer 54and the upper end of the second contact plug layers 55 a-55 g are formedin alignment with the upper surface of the interlayer insulating layer44. As shown in FIGS. 7A and 7B, the first contact plug layer 54 and thesecond contact plug layers 55 a-55 g have in common that the diameter ofthe lower end of each thereof is substantially a diameter φ1. Incontrast, the first contact plug layer 54 and the second contact pluglayers 55 a-55 g have a diameter at upper end thereof that differs fromone another, i.e., φ2 and φ2 a to φ2 g (φ2<φ2 a<φ2 b<φ2 c<φ2 d<φ2 e<φ2f<φ2 g).

To express the above-described configuration in other words, the firstand second contact plug layers 54 and 55 a-55 g are formed such that thegreater a length thereof in the stacking direction, the larger thediameter of the upper end thereof. The diameter φ2 g of the upper end ofthe second contact plug layer 55 g is larger than the diameter φ2 f ofthe upper end of the second contact plug layer 55 f. The diameter φ2 fof the upper end of the second contact plug layer 55 f is larger thanthe diameter φ2 e of the upper end of the second contact plug layer 55e. The diameter φ2 e of the upper end of the second contact plug layer55 e is larger than the diameter φ2 d of the upper end of the secondcontact plug layer 55 d. The diameter φ2 d of the upper end of thesecond contact plug layer 55 d is larger than the diameter φ2 c of theupper end of the second contact plug layer 55 c. The diameter φ2 c ofthe upper end of the second contact plug layer 55 c is larger than thediameter φ2 b of the upper end of the second contact plug layer 55 b.The diameter φ2 b of the upper end of the second contact plug layer 55 bis larger than the diameter φ2 a of the upper end of the second contactplug layer 55 a. The diameter φ2 a of the upper end of the secondcontact plug layer 55 a is larger than the diameter φ2 of the upper endof the first contact plug layer 54.

(Method of Manufacturing the Nonvolatile Semiconductor Memory Device 100in Accordance with the First Embodiment)

Next, a method of manufacturing the nonvolatile semiconductor memorydevice 100 in accordance with the first embodiment is described withreference to FIGS. 8-28. FIGS. 8-28 are cross-sectional views showing amanufacturing process of the nonvolatile semiconductor memory device 100in accordance with the first embodiment.

First, silicon oxide (SiO₂), polysilicon (p-Si), and silicon oxide(SiO₂) are deposited on the upper surface of the semiconductor substrateBa to form the source side first insulating layer 21, the source sideconductive layer 22, and the source side second insulating layer 23, asshown in FIG. 8. Next, the source side hole 26 is formed so as topenetrate the source side first insulating layer 21, the source sideconductive layer 22, and the source side second insulating layer 23, asshown in FIG. 9. Then, silicon oxide (SiO₂) and polysilicon (p-Si) aredeposited on the side wall facing the source side hole 26 to form thesource side gate insulating layer 27 and the source side columnarsemiconductor layer 28, as shown in FIG. 10. Through the above-describedprocesses, the source side select transistor layer 20 is formed.

Next, polysilicon (p-Si) and silicon oxide (SiO₂) are alternatelydeposited to form the word line conductive layers 31 a-31 d and theinter-word line insulating layers 32 a-32 d, as shown in FIG. 11. Then,the memory hole 35 is formed so as to penetrate the word line conductivelayers 31 a-31 d and the inter-word line insulating layers 32 a-32 d, asshown in FIG. 12. Next, silicon oxide (SiO₂), silicon nitride (SiN),silicon oxide (SiO₂), and polysilicon (p-Si) are deposited on the sidewall facing the memory hole 35 to form the memory gate insulating layer36 and the memory columnar semiconductor layer 37, as shown in FIG. 13.Through the above-described processes, the memory transistor layer 30 isformed.

Subsequently, processes similar to those of above-described FIGS. 8-10are performed, thereby forming the drain side select transistor layer40, as shown in FIG. 14.

Next, resist 61 is formed on an upper layer of the drain side insulatinglayer 42, as shown in FIG. 15. The resist 61 is formed so that a portionof the upper surface of the drain side insulating layer 42 is exposed.Then, an etching is performed using the resist 61 as a mask, as shown inFIG. 16. Through this process, the portion of the drain side insulatinglayer 42 and the drain side conductive layer 41 not covered by theresist 61 is removed. Next, a slimming of the resist 61 in the rowdirection is performed, as shown in FIG. 17. Subsequently, an etching isperformed, thereby removing a portion of the drain side insulating layer42 and the drain side conductive layer 41 and a portion of theinter-word line insulating layer 32 d and the word line conductive layer31 d not covered by the resist 61, as shown in FIG. 18. Then, theprocesses shown in FIGS. 17 and 18 are repeatedly performed, whereby astacking structure shown in FIG. 19 configuring the stepped portion STis formed.

Next, the resist 61 is removed, as shown in FIG. 20. Then, CMP (ChemicalMechanical Polishing) is performed after depositing silicon nitride(SiN) and silicon oxide (SiO2), thereby forming the protectiveinsulating layers 24, 33, and 43, and the interlayer insulating layers25, 34, and 44, as shown in FIG. 21.

Subsequently, resist 62 is formed on the upper surface of the interlayerinsulating layer 44, as shown in FIG. 22. The resist 62 includes holes63 and 64 a-64 g. The resist 62 (holes 63 and 64 a-64 g) is for formingthe aforementioned holes 57 and 58 a-58 g. The hole 63 is positioneddirectly above the drain side columnar semiconductor layer 47. The hole64 a (not shown) is positioned directly above the step ST5 of the drainside conductive layer 41. The hole 64 b is positioned directly above thestep ST4 of the word line conductive layer 31 d. The hole 64 c ispositioned directly above the step ST3 of the word line conductive layer31 c. The hole 64 d is positioned directly above the step ST2 of theword line conductive layer 31 b. The hole 64 e is positioned directlyabove the step ST1 of the word line conductive layer 31 a. The hole 64 fis positioned directly above the step ST0 of the source side conductivelayer 22. The hole 64 g is positioned in a region where the layers 20-40are not formed.

Next, an etching is performed using the resist 62 as a mask, as shown inFIG. 23. Through this process, the holes 57 and 58 a-58 g (symbol 58 anot shown) corresponding to the holes 63 and 64 a-64 g are formed.

Then, after removing the resist 62, a layer 65A is deposited on a sidesurface of the holes 57 and 58 a-58 g, as shown in FIG. 24. The layer65A is constituted by a metal such as tantalum (Ta), titanium (Ti),tungsten (W), ruthenium (Ru), or manganese (Mn), or from a metalcompound thereof. The layer 65A is formed by sputtering or CVD.Additionally as shown in FIG. 24, a layer 65B is deposited on the layer65A so as to fill the holes 57 and 58 a-58 g. The layer 65B isconstituted by any of tungsten (W), copper (Cu), and aluminum (Al).

Next, CMP is performed to remove a portion of the layers 65A and 65Bformed on the holes 57 and 58 a-58 g, thereby forming the first contactplug layer 54 and the second contact plug layers 55 a-55 g, as shown inFIG. 25.

Subsequently, silicon oxide (SiO₂) is deposited to form the interlayerinsulating layer 51, as shown in FIG. 26. Further as shown in FIG. 26, aresist 66 is formed on an upper surface of the interlayer insulatinglayer 51. The resist 66 includes a trench 66A. The resist 66 (trench66A) is for forming the aforementioned trench 56.

Next, an etching is performed using the resist 66 as a mask, as shown inFIG. 27. Through this process, the trench 56 corresponding to the trench66A is formed.

Then, after removing the resist 66, a layer 67A is deposited on a sidesurface facing the trench 56, as shown in FIG. 28. The layer 67A isconstituted by a metal such as tantalum (Ta), titanium (Ti), tungsten(W), ruthenium (Ru), or manganese (Mn), or from a metal compoundthereof. The layer 67A is formed by sputtering or CVD. Additionally asshown in FIG. 28, a layer 67B is deposited on the layer 67A so as tofill the trench 56. The layer 67B is constituted by any of tungsten (W),copper (Cu), and aluminum (Al).

Then, CMP is performed to remove a portion of the layers 67A and 67Bformed on the trench 56. Subsequently, the first wiring layer 52 and thesecond wiring layers 53 a-53 g are formed, thereby completing formationof the nonvolatile semiconductor memory device 100 in accordance withthe first embodiment shown in FIGS. 4 and 5.

(Advantages of the Nonvolatile Semiconductor Memory Device 100 inAccordance with the First Embodiment)

Next, advantages of the nonvolatile semiconductor memory device 100 inaccordance with the first embodiment are described. The nonvolatilesemiconductor memory device 100 in accordance with the first embodimentis capable of a high degree of integration as shown in theabove-described stacking structure.

To describe the advantages of the nonvolatile semiconductor memorydevice 100 in accordance with the first embodiment, a comparativeexample is here considered. A nonvolatile semi conductor memory devicein accordance with the comparative example includes a first contact pluglayer and a plurality of second contact plug layers formed in a taperedshape in which a diameter thereof decreases from an upper end thereof toa lower end thereof. A length in the stacking direction of each of theplurality of second contact plug layers differs from one another.Moreover, all of the first and second contact plug layers has the samediameter at the upper ends thereof, but each have a diameter at thelower end thereof different from one another.

Thus, in the comparative example, a contact resistance of the secondcontact plug layers is non-uniform, due to difference in diameter of thelower end thereof.

Additionally in the comparative example, an etching speed (processingrate) during manufacture is uniform for all of the holes. Accordingly,in the above-described structure of the comparative example, it isdifficult to perform etching of holes having depths equal to desiredlengths of the second contact plug layers in the stacking direction.

That is, the holes are sometimes formed penetrating a desired word lineconductive layer. Or, the holes sometimes do not reach the desired wordline conductive layer.

Moreover, in the comparative example, the longer the second contact pluglayer in the stacking direction, the smaller the diameter of the lowerend thereof. That is, the longer the second contact plug layer in thestacking direction, the more difficult it becomes, during manufacture,to fill the hole with a conductive layer. Accordingly, voids (emptyholes) are formed in the second contact plug layer causing the likes ofpoor conductivity or a large rise in the contact resistance.

In contrast, the nonvolatile semiconductor memory device 100 inaccordance with the first embodiment includes the first contact pluglayer 54 and the second contact plug layers 55 a-55 g formed in atapered shape in which the diameter thereof decreases from the upper endthereof to the lower end thereof. The first contact plug layer 54 andthe second contact plug layers 55 a-55 g have in common that thediameter of the lower end of each thereof is substantially a diameterφ1. In contrast, the first contact plug layer 54 and the second contactplug layers 55 a-55 g have a diameter of the upper end differing fromone another, i.e., φ2 and φ2 a-φ2 g (φ2<2 a<φ2 b<φ2 c<φ2 d<φ2 e<φ2 f<φ2g).

That is, in the first embodiment, the first contact plug layer 54 andthe second contact plug layers 55 a-55 g are configured having a uniformcontact area with each of the diffusion layer Ba1, the source sideconductive layer 22, the word line conductive layers 31 a-31 d, thedrain side conductive layer 41, and the drain side columnarsemiconductor layer 47. The nonvolatile semiconductor memory device inaccordance with the first embodiment thus has a more uniform contactresistance than the above-described comparative example.

Additionally in the first embodiment, a diameter of the upper end of theholes 57 and 58 a-58 g is set so that it corresponds to the length ofthe first contact plug layer 54 and the second contact plug layers 55a-55 g in the stacking direction. Here, the larger the diameter of theupper end of the holes 57 and 58 a-58 g, the faster the processing rate(speed) due to a loading effect of RIE. That is, in the firstembodiment, the diameter of the upper end of the holes 57 and 58 a-58 gis used to regulate the processing rate, and, as a result, duringmanufacture, the holes 57 and 58 a-58 g can be formed to a desired depthwith more certainty than in the above-described comparative example.

Further, in the first embodiment, a diameter of the lower end of theholes 57 and 58 a-58 g is equal to one another. Accordingly, in thenonvolatile semiconductor memory device in accordance with the firstembodiment, filling of the holes 57 and 58 a-58 g during manufacture canbe performed more easily than in the above-described comparativeexample, thereby enabling suppression of poor conductivity or a largerise in the contact resistance.

As is clear from the above, the nonvolatile semiconductor memory device100 in accordance with the first embodiment can ensure a higherreliability compared to the comparative example.

Second Embodiment

(Configuration of a Nonvolatile Semiconductor Memory Device inAccordance with a Second Embodiment)

Next, a configuration of a nonvolatile semiconductor memory device inaccordance with a second embodiment is described with reference to FIG.29. FIG. 29 is a cross-sectional view showing the nonvolatilesemiconductor memory device in accordance with the second embodiment.Note that in the second embodiment, identical symbols are assigned toconfigurations similar to those in the first embodiment and descriptionsthereof are omitted.

The nonvolatile semiconductor memory device in accordance with thesecond embodiment includes a wiring layer 50′ which differs from that ofthe first embodiment. The wiring layer 50′ differs from the firstembodiment (single-damascene structure) in having a dual-damascenestructure. The wiring layer 50′ includes a trench 56′ which differs fromthat of the first embodiment. A width of the trench 56′ in the rowdirection is formed larger than a diameter of each of the holes 57 and58 a-58 g. Further, the wiring layer 50′ includes a layer 52′ in placeof the first wiring layer and first contact plug layer 54 in the firstembodiment. In addition, the wiring layer 50′ includes layers 53 a′-53g′ in place of the second wiring layers 53 a-53 g and second contactplug layers 55 a-55 g in the first embodiment.

The layer 52′ is formed so as to fill the hole 57 and the trench 56′ ina continuous and integrated manner. The layer 52′ includes a barriermetal layer 2A′ and a metal layer 2B′. The barrier metal layer 2A′ isformed in a continuous and integrated manner with a certain thickness ona side surface of the hole 57 and the trench 56′. The metal layer 2B′ isformed so as to be in contact with the barrier metal layer 2A′ and tofill the hole 57 and the trench 56′ in a continuous and integratedmanner.

The layers 53 a′-53 g′ are formed so as to fill the holes 58 a-58 g andthe trench 56′ in a continuous and integrated manner. The layers 53a′-53 g′ include barrier metal layers 3 aA′-3 gA′ and metal layers 3aB′-3 gB′. The barrier metal layers 3 aA′-3 gA′ are formed in acontinuous and integrated manner with a certain thickness on a sidesurface of the holes 58 a-58 g and the trench 56′. The metal layers 3aB′-3 gB′ are formed so as to be in contact with the barrier metallayers 3 aA′-3 gA′ and to fill the holes 58 a-58 g and the trench 56′ ina continuous and integrated manner.

The barrier metal layers 2A′ and 3 aA′-3 gA′ are constituted from ametal such as tantalum (Ta), titanium (Ti), tungsten (W), ruthenium(Ru), or manganese (Mn), or from a metal compound thereof. The metallayers 2B′ and 3 aB′-3 gB′ are constituted by any of tungsten (W),copper (Cu), and aluminum (Al).

(Method of Manufacturing the Nonvolatile Semiconductor Memory Device inAccordance with the Second Embodiment)

Next, a method of manufacturing the nonvolatile semiconductor memorydevice in accordance with the second embodiment is described withreference to FIGS. 30-38. FIGS. 30-38 are cross-sectional views showinga manufacturing process of the nonvolatile semiconductor memory devicein accordance with the second embodiment.

First, processes up to the process shown in FIG. 21 of the firstembodiment are executed. Then, silicon oxide (SiO₂) is deposited on theinterlayer insulating layer 44 to form the interlayer insulating layer51, as shown in FIG. 30.

Next, resist 68 is formed on an upper surface of the interlayerinsulating layer 51, as shown in FIG. 31. The resist 68 includes a hole68A. The resist 68 (hole 68A) is for forming the aforementioned holes 57and 58 a-58 g.

Next, an etching is performed using the resist 68 as a mask, as shown inFIG. 32. Through this process, the holes 57 and 58 a-58 g (symbol 58 anot shown) corresponding to the hole 68A are formed. In addition, a hole51A is formed so as to penetrate the interlayer insulating layer 51. Thehole 51A is formed in a continuous and integrated manner with the hole57. The hole 51A is formed in a continuous and integrated manner witheach of the holes 58 a-58 g. Note that the resist 68 is removed afterthe etching.

Subsequently, an organic-based material is deposited so as to fill theholes 51A, 57, and 58 a-58 g, thereby forming a sacrifice layer 69, asshown in FIG. 33. Next, silicon oxide (SiO₂) is deposited on thesacrifice layer 69 to form a stacking mask 70, as shown in FIG. 34. Thestacking mask 70 is used for lithography and RIE processing of an upperlayer wiring.

Then, resist 71 is formed on an upper surface of the stacking mask 70,as shown in FIG. 35. The resist 71 includes a trench 71A. The resist 71(trench 71A) is used to form the aforementioned trench 56′.

Next, an etching is performed using the resist 71 as a mask, as shown inFIG. 36. Through this process, a trench 56′ corresponding to the trench71A is formed. In addition, a trench 72 is formed so as to penetrate thestacking mask 70 and the sacrifice layer 69 formed therebelow. Thetrench 72 is formed in a continuous and integrated manner with thetrench 56′.

Subsequently, the stacking mask 70 and the sacrifice layer 69 areremoved, as shown in FIG. 37. Next, a layer 73A is deposited in acontinuous and integrated manner on a side surface of the holes 57 and58 a-58 g, and the trench 56′, as shown in FIG. 38. The layer 73A isconstituted by a metal such as tantalum (Ta), titanium (Ti), tungsten(W), ruthenium (Ru), or manganese (Mn), or from a metal compoundthereof. Furthermore, as shown in FIG. 38, a layer 73B is deposited onthe layer 73A so as to fill the holes 57 and 58 a-58 g, and the trench56′. The layer 73B is constituted by any of tungsten (W), copper (Cu),and aluminum (Al). Then, CMP is performed, similarly to the firstembodiment, thereby completing formation of the nonvolatilesemiconductor memory device in accordance with the second embodimentshown in FIG. 29.

(Advantages of the Nonvolatile Semiconductor Memory Device in Accordancewith the Second Embodiment)

Next, advantages of the nonvolatile semiconductor memory device inaccordance with the second embodiment are described. The nonvolatilesemiconductor memory device in accordance with the second embodimentincludes similar features to the first embodiment, and displays similaradvantages to the first embodiment.

The nonvolatile semiconductor memory device in accordance with the firstembodiment here includes the first and second contact plug layers 54 and55 a-55 g in the holes 57 and 58 a-58 g, and the first and second wiringlayers 52 and 53 a-53 g in the trench 56.

In contrast, the nonvolatile semiconductor memory device in accordancewith the second embodiment includes the layer 52′ and the layers 53a′-53 g′ formed in a continuous and integrated manner with the holes 57and 58 a-58 g, and the trench 56′. Accordingly, in the secondembodiment, the barrier metal layer is not formed in a bottom of thetrench 56′. Thus, the nonvolatile semiconductor memory device inaccordance with the second embodiment enables the contact resistance tobe lowered more than in the first embodiment.

In addition, the method of manufacturing the nonvolatile semiconductormemory device in accordance with the second embodiment forms the layer52′ and the layers 53 a′-53 g′ in a continuous and integrated mannerwith the holes 57 and 58 a-58 g, and the trench 56′. Thus, in the methodof manufacturing the nonvolatile semiconductor memory device inaccordance with the second embodiment, a number of processes can bereduced and a manufacturing cost thereby lowered more than in the firstembodiment.

Note that in the second embodiment a width of the trench 56′ ispreferably made identical to or greater than the diameter of the upperend of the holes 57 and 58 a-58 g. This is because, by so doing, thelayer 52′ and the layers 53 a′-53 g′ can be easily formed in acontinuous and integrated manner with the holes 57 and 58 a-58 g, andthe trench 56′.

Third Embodiment

(Configuration of a Nonvolatile Semiconductor Memory Device inAccordance with a Third Embodiment)

Next, a configuration of a nonvolatile semiconductor memory device inaccordance with a third embodiment is described with reference to FIG.39. FIG. 39 is a cross-sectional view showing the nonvolatilesemiconductor memory device in accordance with the third embodiment.Note that in the third embodiment, identical symbols are assigned toconfigurations similar to those in the first and second embodiments anddescriptions thereof are omitted.

The nonvolatile semiconductor memory device in accordance with the thirdembodiment includes a wiring layer 50″ which differs from those of thefirst and second embodiments. The wiring layer 50″ includes a firstcontact plug layer 54′ and second contact plug layers 55 a′-55 g′ whichdiffer from those of the first embodiment.

The first contact plug layer 54′ and the second contact plug layers 55a′-55 g′ each have a different diameter and are formed such that anaspect ratio (height of layer/diameter of lower end of layer) isconstant. That is, a diameter of a lower end of the first contact pluglayer 54′ and the second contact plug layers 55 a′-55 g′ (φ1′<φ1 a′<φ1b′<φ1 c′<φ1 d′<φ1 e′<φ1 f′<φ1 g′) is determined by the height of therespective layer. In addition, the first contact plug layer 54′ and thesecond contact plug layers 55 a′-55 g′ are formed in a tapered shapehaving a common inclination angle.

Accordingly, a diameter of an upper end of the first contact plug layer54′ and the second contact plug layers 55 a′-55 g′ (φ2′<φ2 a′<φ2 b′<φ2c′<φ2 d′<φ2 e′<φ2 f′<φ2 g′) is determined by the diameter of therespective lower end.

Note that the first contact plug layer 54′ and the second contact pluglayers 55 a′-55 g′ are formed so as to fill holes 57′ and 58 a′-58 g′which differ from those of the first embodiment. Moreover, the firstcontact plug layer 54′ and the second contact plug layers 55 a′-55 g′include barrier metal layers 4A′ and 5 aA′-5 gA′ and metal layers 4B′and 5 aB′-5 gB′, similarly to the first embodiment.

(Advantages of the Nonvolatile Semiconductor Memory Device in Accordancewith the Third Embodiment)

Next, advantages of the nonvolatile semiconductor memory device inaccordance with the third embodiment are described. The nonvolatilesemiconductor memory device in accordance with the third embodimentincludes similar features to the first embodiment, and displays similaradvantages to the first embodiment.

In addition, the nonvolatile semiconductor memory device in accordancewith the third embodiment includes the first contact plug layer 54′ andthe second contact plug layers 55 a′-55 g′ formed such that the aspectratio (height of layer/diameter of lower end of layer) is constant. Thefirst contact plug layer 54′ and the second contact plug layers 55 a′-55g′ here have a resistance which is determined by a length in thestacking direction and a cross-sectional area thereof. Consequently, inthe nonvolatile semiconductor memory device in accordance with the thirdembodiment, a shape resulting from the above-described aspect ratioenables the contact resistance, which includes the resistance of thefirst contact plug layer 54′ and the second contact plug layers 55 a′-55g′ themselves, to be made uniform.

Fourth Embodiment

(Configuration of a Nonvolatile Semiconductor Memory Device inAccordance with a Fourth Embodiment)

Next, a configuration of a nonvolatile semiconductor memory device inaccordance with a fourth embodiment is described with reference to FIG.40. FIG. 40 is a cross-sectional view showing the nonvolatilesemiconductor memory device in accordance with the fourth embodiment.Note that in the fourth embodiment, identical symbols are assigned toconfigurations similar to those in the first through third embodimentsand descriptions thereof are omitted.

The nonvolatile semiconductor memory device in accordance with thefourth embodiment includes a stepped portion STa which differs from thatof the first embodiment, as shown in FIG. 40. The stepped portion STaincludes steps STa0-STa5 which differ from those of the firstembodiment. The step STa0 is configured by the end in the row directionof the source side first insulating layer 21, the source side conductivelayer 22, and the source side second insulating layer 23, similarly tothe first embodiment. In addition, the steps STa1-STa4 are configured bythe end in the row direction of the word line conductive layers 31 a-31d and the inter-word line insulating layers 32 a-32 d. Further, the stepSTa5 is configured by the end in the row direction of the drain sideconductive layer 41 and the drain side insulating layer 42.

The steps STa0-STa4 have a width in the row direction which differs fromone another, namely certain widths L20-L24 (L20>L21>L22>L23>L24). Thatis, the width L20 of the step STa0 is greater than the width L21 of thestep STa1 (layer above the step STa0); the width L21 of the step STa1 isgreater than the width L22 of the step STa2 (layer above the step STa1);the width L22 of the step STa2 is greater than the width L23 of the stepSTa3 (layer above the step STa2); and the width L23 of the step STa3 isgreater than the width L24 of the step STa4 (layer above the step STa3).

(Advantages of the Nonvolatile Semiconductor Memory Device in Accordancewith the Fourth Embodiment)

The nonvolatile semiconductor memory device in accordance with thefourth embodiment includes the steps STa0-STa4 having the certain widthsL20-L24 (L20>L21>L22>L23>L24). Thus, in the nonvolatile semiconductormemory device in accordance with the fourth embodiment, the secondcontact plug layers 55 b-55 g can be disposed with a sufficient spacingtherebetween, compared with the first embodiment. As a result, a shortcircuit caused by mutual contact of the second contact plug layers 55b-55 g can be curbed in the nonvolatile semiconductor memory device inaccordance with the fourth embodiment. That is, the nonvolatilesemiconductor memory device in accordance with the fourth embodiment canbe made more reliable than the first embodiment.

More specifically, when a number of the steps stacked increases, it mayhappen that lithography becomes impossible, due to adjacent secondcontact plug layers overlapping with each other. Moreover, if the secondcontact plug layers, although not overlapping, are too close to eachother, there is a possibility that lithography resolution is reduced andpatterning cannot be successfully performed. Furthermore, in the casethat the second contact plug layers are too close to each other, itbecomes impossible to dispose a dummy auxiliary pattern to improve thelithography resolution, thereby lowering the lithography resolution inthis case also. The above problems can be solved by the nonvolatilesemiconductor memory device in accordance with the fourth embodiment,since a physical spacing of the second contact plug layers 55 b-55 g canbe set as described above.

Fifth Embodiment

(Configuration of a Nonvolatile Semiconductor Memory Device inAccordance with a Fifth Embodiment)

Next, a configuration of a nonvolatile semiconductor memory device inaccordance with a fifth embodiment is described with reference to FIG.41. FIG. 41 is a top view showing second contact plug layers 55Ab-55Agin the nonvolatile semiconductor memory device in accordance with thefifth embodiment. Note that in the fifth embodiment, identical symbolsare assigned to configurations similar to those in the first throughfourth embodiments and descriptions thereof are omitted.

The nonvolatile semiconductor memory device in accordance with the fifthembodiment includes the second contact plug layers 55Ab-55Ag whichdiffer from those of the first and second embodiments, as shown in FIG.41. The second contact plug layers 55Ab-55Ag are disposed such that anupper end thereof is arranged in a line along a direction (arrow A)different to the row direction, as viewed from a planar direction.

(Advantages of the Nonvolatile Semiconductor Memory Device in Accordancewith the Fifth Embodiment)

The nonvolatile semiconductor memory device in accordance with the fifthembodiment displays similar advantages to the first embodiment. Inaddition, the nonvolatile semiconductor memory device in accordance withthe fifth embodiment includes the second contact plug layers 55Ab-55Agarranged in a line in a direction at a certain angle to the rowdirection. Thus, in the nonvolatile semiconductor memory device inaccordance with the fifth embodiment, the second contact plug layers55Ab-55Ag can be disposed with a sufficient spacing therebetween,compared with the first embodiment. Accordingly, it is possible to curba short circuit that may occur between the second contact plug layersand to improve the lithography resolution in the nonvolatilesemiconductor memory device in accordance with the fifth embodiment. Thenonvolatile semiconductor memory device in accordance with the fifthembodiment can thus be made more reliable than the first embodiment.

Sixth Embodiment

(Configuration of a Nonvolatile Semiconductor Memory Device inAccordance with a Sixth Embodiment)

Next, a configuration of a nonvolatile semiconductor memory device inaccordance with a sixth embodiment is described with reference to FIG.42. FIG. 42 is a top view showing the second contact plug layers55Ab-55Ag in the nonvolatile semiconductor memory device in accordancewith the sixth embodiment. Note that in the sixth embodiment, identicalsymbols are assigned to configurations similar to those in the firstthrough fifth embodiments and descriptions thereof are omitted.

The nonvolatile semiconductor memory device in accordance with the sixthembodiment includes the steps STa0-STa4 similar to those of the fourthembodiment, as shown in FIG. 42. The nonvolatile semiconductor memorydevice in accordance with the sixth embodiment differs from the fifthembodiment in this point. Note that other configurations of the sixthembodiment are similar to the fifth embodiment.

(Advantages of the Nonvolatile Semiconductor Memory Device in Accordancewith the Sixth Embodiment)

The nonvolatile semiconductor memory device in accordance with the sixthembodiment includes similar features to the fifth embodiment, anddisplays similar advantages to the fifth embodiment. In addition, thenonvolatile semiconductor memory device in accordance with the sixthembodiment includes the steps STa0-STa4, whereby an occupied area can bereduced and a contact of the second contact plug layers 55Ab-55Ag can becurbed, similarly to the fourth embodiment.

Seventh Embodiment

(Configuration of a Nonvolatile Semiconductor Memory Device inAccordance with a Seventh Embodiment)

Next, a configuration of a nonvolatile semiconductor memory device inaccordance with a seventh embodiment is described with reference toFIGS. 43 and 44. FIG. 43 is a top view showing second contact pluglayers 55Bb-55Bg in the nonvolatile semiconductor memory device inaccordance with the seventh embodiment. FIG. 44 is a top view showingsecond wiring layers 53Ab-53Ag in the nonvolatile semiconductor memorydevice in accordance with the seventh embodiment. Note that in theseventh embodiment, identical symbols are assigned to configurationssimilar to those in the first through sixth embodiments and descriptionsthereof are omitted.

The nonvolatile semiconductor memory device in accordance with theseventh embodiment includes steps STb0-STb4 and the second contact pluglayers 55Bb-55Bg which differ from those of the first through fifthembodiments, as shown in FIG. 43. The second contact plug layers55Bb-55Bg are disposed so as to be arranged in a line in a direction ata certain angle to the row direction, similarly to the fifth and sixthembodiments. A lower end of the second contact plug layers 55Bb-55Bg isprovided in the steps STb0-STb4. At the same time, an upper end of thesecond contact plug layers 55Bb-55Bg is formed so as to protrude in therow direction from a region directly above where the steps STb0-STb4 areprovided.

In addition, the nonvolatile semiconductor memory device in accordancewith the seventh embodiment includes the second wiring layers 53Ab-53Agwhich differ from those of the first through sixth embodiments, as shownin FIG. 44. The second wiring layers 53Ab-53Ag are formed in stripesextending in the row direction and having a certain pitch in the columndirection.

(Advantages of the Nonvolatile Semiconductor Memory Device in Accordancewith the Seventh Embodiment)

The nonvolatile semiconductor memory device in accordance with theseventh embodiment displays similar advantages to the nonvolatilesemiconductor memory device in accordance with the fifth and sixthembodiments. In addition, in the nonvolatile semiconductor memory devicein accordance with the seventh embodiment, the upper end of the secondcontact plug layers 55Bb-55Bg is formed so as to protrude from theregion directly above where the steps STb0-STb4 are provided. Thus, inthe nonvolatile semiconductor memory device in accordance with theseventh embodiment, the second contact plug layers 55Bb-55Bg can bedisposed with a more compacted spacing in the row direction than in thefifth and sixth embodiments, thereby reducing an occupied area.

Eighth Embodiment

(Configuration of a Nonvolatile Semiconductor Memory Device inAccordance with an Eighth Embodiment)

Next, a configuration of a nonvolatile semiconductor memory device inaccordance with an eighth embodiment is described with reference to FIG.45. FIG. 45 is a top view showing second wiring layers 53Bb-53Bg in thenonvolatile semiconductor memory device in accordance with the eighthembodiment. Note that in the eighth embodiment, identical symbols areassigned to configurations similar to those in the first through seventhembodiments and descriptions thereof are omitted.

The nonvolatile semiconductor memory device in accordance with theeighth embodiment includes the second wiring layers 53Bb-53Bg whichdiffer from those of the seventh embodiment. The eighth embodimentdiffers from the seventh embodiment in this point, but is similar to theseventh embodiment regarding other configurations.

The second wiring layers 53Bb-53Bg are formed in an L-shape as viewedfrom above, as shown in FIG. 45. That is, the second wiring layers53Bb-53Bg are formed so as to extend from a leading end in contact withthe second wiring layers 53Bb-53Bg to a certain position in the rowdirection, and so as to extend from the certain position in the columndirection.

(Advantages of the Nonvolatile Semiconductor Memory Device in Accordancewith the Eighth Embodiment)

The nonvolatile semiconductor memory device in accordance with theeighth embodiment includes similar features to the seventh embodiment,and displays similar advantages to the seventh embodiment.

Ninth Embodiment

(Configuration of a Nonvolatile Semiconductor Memory Device inAccordance with a Ninth Embodiment)

Next, a configuration of a nonvolatile semiconductor memory device inaccordance with a ninth embodiment is described with reference to FIG.46. FIG. 46 is a top view showing second contact plug layers 55Cb-55Cgin the nonvolatile semiconductor memory device in accordance with theninth embodiment. Note that in the ninth embodiment, identical symbolsare assigned to configurations similar to those in the first througheighth embodiments and descriptions thereof are omitted.

The nonvolatile semiconductor memory device in accordance with the ninthembodiment includes the second contact plug layers 55Cb-55Cg whichdiffer from those of the first through eighth embodiments, as shown inFIG. 46. The second contact plug layers 55Cb-55Cg are disposed in azigzag shape centered on the row direction.

(Advantages of the Nonvolatile Semiconductor) Memory Device inAccordance with the Ninth Embodiment

The nonvolatile semiconductor memory device in accordance with the ninthembodiment displays similar advantages to the fifth and sixthembodiments.

Tenth Embodiment

(Configuration of a Nonvolatile Semiconductor Memory Device inAccordance with a Tenth Embodiment)

Next, a configuration of a nonvolatile semiconductor memory device inaccordance with a tenth embodiment is described with reference to FIG.47. FIG. 47 is a top view showing the second contact plug layers55Cb-55Cg in the nonvolatile semiconductor memory device in accordancewith the tenth embodiment. Note that in the tenth embodiment, identicalsymbols are assigned to configurations similar to those in the firstthrough ninth embodiments and descriptions thereof are omitted.

The nonvolatile semiconductor memory device in accordance with the tenthembodiment includes the steps STa0-STa4 similar to those of the fourthembodiment, as shown in FIG. 47. The nonvolatile semiconductor memorydevice in accordance with the tenth embodiment differs from the ninthembodiment in this point. Note that other configurations of the tenthembodiment are similar to the ninth embodiment.

(Advantages of the Nonvolatile Semiconductor Memory Device in Accordancewith the Tenth Embodiment)

The nonvolatile semiconductor memory device in accordance with the tenthembodiment includes similar features to the ninth embodiment, anddisplays similar advantages to the ninth embodiment. In addition, thenonvolatile semiconductor memory device in accordance with the tenthembodiment includes the steps STa0-STa4, whereby an occupied area can bereduced and a contact of the second contact plug layers 55Cb-55Cg can becurbed, similarly to the fourth embodiment.

Other Embodiments

This concludes description of embodiments of the nonvolatilesemiconductor memory device in accordance with the present invention,but it should be noted that the present invention is not limited to theabove-described embodiments, and that various alterations, additions,substitutions, and so on, are possible within a range not departing fromthe scope and spirit of the invention. For example, the memory columnarsemiconductor layer 37 is not limited to the column shape, and may beU-shaped. A U-shaped memory columnar semiconductor layer 37 includes apair of columnar portions and a joining portion configured to join alower end of the columnar portions.

1. A nonvolatile semiconductor memory device, comprising: a memorystring having a plurality of electrically rewritable memory cellsconnected in series; and a wiring connected to a control electrode ofthe memory cells, the memory string comprising: a semiconductor layerincluding a columnar portion extending in a perpendicular direction withrespect to a substrate; a charge storage layer formed on a side surfaceof the columnar portion; and a plurality of first conductive layersformed on the charge storage layer, and configured to function as acontrol electrode of the memory cells, the plurality of first conductivelayers comprising a stepped portion formed in a stepped shape such thatpositions of ends of the plurality of first conductive layers differfrom one another, and the wiring comprising a plurality of secondconductive layers extending upwardly from an upper surface of the firstconductive layers comprising the stepped portion, the plurality ofsecond conductive layers being formed such that upper ends thereof arealigned with a surface parallel to the substrate, and such that adiameter thereof decreases from the upper end thereof to a lower endthereof, and the plurality of second conductive layers being formed suchthat the greater a length thereof in the perpendicular direction, thelarger a diameter of the upper end thereof.
 2. The nonvolatilesemiconductor memory device according to claim 1, wherein stepsconfiguring the stepped portion includes a first step positioned at afirst position and a second step positioned at a second position in ahigher layer than the first position, the first step having a largerwidth than that of the second step.
 3. The nonvolatile semiconductormemory device according to claim 1, wherein sides of steps configuringthe stepped portion face a first direction parallel to the substrate,and the plurality of second conductive layers are arranged along asecond direction parallel to the substrate.
 4. The nonvolatilesemiconductor memory device according to claim 1, wherein sides of stepsconfiguring the stepped portion face a first direction parallel to thesubstrate, and the plurality of second conductive layers are disposed ina zigzag shape centered on the first direction.
 5. The nonvolatilesemiconductor memory device according to claim 1, wherein a ratio of aheight of the second conductive layer and a diameter of a lower end ofthe second conductive layer is constant among the plurality of secondconductive layers.
 6. The nonvolatile semiconductor memory deviceaccording to claim 1, wherein a lower end of the second conductive layeris formed so as to be in contact with a step included the steppedportion, and an upper end of the second conductive layer is formed so asto protrude from the step with which the lower end is in contact, withregard to a direction parallel to the substrate.
 7. The nonvolatilesemiconductor memory device according to claim 1, further comprising: aplurality of third conductive layers respectively in contact with theupper end of the plurality of second conductive layers, wherein theplurality of third conductive layers are formed continuously in anintegrated manner with the second conductive layer and extending in adirection parallel to the substrate.
 8. The nonvolatile semiconductormemory device according to claim 3, further comprising: a plurality ofthird conductive layers respectively in contact with the upper end ofthe plurality of second conductive layers, wherein the plurality ofthird conductive layers are formed in stripes extending in the firstdirection and having a pitch in a third direction orthogonal to thefirst direction.
 9. The nonvolatile semiconductor memory deviceaccording to claim 3, further comprising: a plurality of thirdconductive layers respectively in contact with the upper end of theplurality of second conductive layers, wherein the plurality of thirdconductive layers are formed so as to extend from a leading end incontact with the plurality of second conductive layers to a position inthe first direction, and so as to extend from the position in a thirddirection orthogonal to the first direction.
 10. A nonvolatilesemiconductor memory device, comprising: a memory string having aplurality of electrically rewritable memory cells connected in series;and a wiring connected to a control electrode of the memory cells, thememory string comprising: a semiconductor layer including a columnarportion extending in a perpendicular direction with respect to asubstrate; a charge storage layer formed on a side surface of thecolumnar portion; and a plurality of first conductive layers formed onthe charge storage layer, and configured to function as a controlelectrode of the memory cells, the plurality of first conductive layerscomprising a stepped portion formed in a stepped shape such thatpositions of ends of the plurality of first conductive layers differfrom one another, and the wiring comprising a plurality of secondconductive layers extending upwardly from an upper surface of the firstconductive layers comprising the stepped portion, the plurality ofsecond conductive layers being formed such that upper ends thereof arealigned with a surface parallel to the substrate, and a ratio of aheight of the second conductive layer and a diameter of a lower end ofthe second conductive layer being constant among the plurality of secondconductive layers.
 11. The nonvolatile semiconductor memory deviceaccording to claim 10, wherein steps configuring the stepped portionincludes a first step positioned at a first position and a second steppositioned at a second position in a higher layer than the firstposition, the first step having a larger width than that of the secondstep.
 12. The nonvolatile semiconductor memory device according to claim10, wherein sides of steps configuring the stepped portion face a firstdirection parallel to the substrate, and the plurality of secondconductive layers are arranged along a second direction parallel to thesubstrate.
 13. The nonvolatile semiconductor memory device according toclaim 10, wherein a side of steps configuring the stepped portion facedto a first direction parallel to the substrate, and the plurality ofsecond conductive layers are disposed in a zigzag shape centered on thefirst direction.
 14. A method of manufacturing a nonvolatilesemiconductor memory device, the nonvolatile semiconductor memory deviceincluding a plurality of memory strings each having a plurality ofelectrically rewritable memory cells connected in series, comprising:depositing a plurality of first conductive layers on a substrate;penetrating the plurality of first conductive layers to form apenetration hole; forming a charge storage layer on a side surface ofthe penetration hole; forming a semiconductor layer so as to fill thepenetration hole; forming a stepped portion formed in a stepped shape inthe plurality of first conductive layers such that positions of ends ofthe plurality of first conductive layers differ from one another; andforming a plurality of second conductive layers extending upwardly froman upper surface of the first conductive layers configuring the steppedportion, the plurality of second conductive layers being formed suchthat upper ends thereof are aligned with a surface parallel to thesubstrate, and such that a diameter thereof decreases from the upper endthereof to a lower end thereof, and being formed such that the greater alength thereof in the perpendicular direction, the larger a diameter ofthe upper end thereof.
 15. The method of manufacturing a nonvolatilesemiconductor memory device according to claim 14, wherein stepsconfiguring the stepped portion includes a first step positioned at afirst position and a second step positioned at a second position in ahigher layer than the first position, the first step having a largerwidth than that of the second step.
 16. The method of manufacturing anonvolatile semiconductor memory device according to claim 14, whereinsides of steps configuring the stepped portion face a first directionparallel to the substrate, and the plurality of second conductive layersare arranged along a second direction parallel to the substrate.
 17. Themethod of manufacturing a nonvolatile semiconductor memory deviceaccording to claim 14, wherein sides of steps configuring the steppedportion face a first direction parallel to the substrate, and theplurality of second conductive layers are disposed in a zigzag shapecentered on the first direction.
 18. The method of manufacturing anonvolatile semiconductor memory device according to claim 14, wherein aratio of a height of the second conductive layer and a diameter of alower end of the second conductive layer is constant among the pluralityof second conductive layers.
 19. The method of manufacturing anonvolatile semiconductor memory device according to claim 14, wherein alower end of the second conductive layer is formed so as to be incontact with a step included the stepped portion, and an upper end ofthe second conductive layer is formed so as to protrude from the stepwith which the lower end is in contact, with regard to a directionparallel to the substrate.
 20. The method of manufacturing a nonvolatilesemiconductor memory device according to claim 14, further comprising:forming a plurality of third conductive layers respectively in contactwith the upper end of the plurality of second conductive layers, whereinthe plurality of third conductive layers are formed continuously in anintegrated manner with the second conductive layer and extending in adirection parallel to the substrate.